There is evidence that kidney stone patients with absorptive hypercalciuria(AH) (who often have spinal osteopenia) and idiopathic osteoporosis patients (who sometimes have AH) may represent "upregulated" states of the 1,25 Vitamin D receptor. The hypothesis to be tested is: enhanced calcitriol synthesis leads to upregulation of 1,25 Vitamin D receptor which leads to sustained upregulated state. AH would ensue if the gut were the primary site of involvement, whereas idiopathic osteoporosis would develop if bone were the key target.